PCB Common Problems And Specific Fault Analysis

#01

Welding problem

Description:

Solder joint problems are one of the most common defects in PCBS, affecting the electrical connection between the component and the board.

Common types:

Cold weld spot: The weld is incomplete or weak, the surface looks dull or cracked, resulting in unreliable electrical contact.

Bridge Welding:Excessive solder is connected to adjacent pins or pads, resulting in short circuit.

Insufficient solder:Too little solder to secure the assembly, resulting in an open circuit.

Stele effect:During reflow welding, due to uneven heating or improper application of solder paste, one side of the assembly lifts up, resembling a tombstone.

The reason:Improper temperature curve of reflow furnace, incorrect application of solder paste or surface contamination.

Impact:Intermittent connection, short circuit or complete circuit failure.

#02

Components are misaligned or faulty

Description:

Components may be mispositioned, misaligned, or inherently defective, interfering with the intended function.

Example:

Misalignment: The component is not properly mounted on the pad due to a placement machine error.

Missing components: Missing parts during assembly, resulting in incomplete circuits.

Defective components: Faulty or counterfeit parts that fail during use.

Causes: Faulty programming of automated assembly machines, poor quality control, or supply chain issues in component procurement.

Impact: The circuit does not operate as designed, resulting in partial or total failure.

#03

The wiring and pad are damaged

Description: 

Copper wiring or pads on the PCB may be damaged, interrupting electrical access.

Common problems:

Line break: Cracks or notches appear in the line due to excessive etching or physical stress

Layering: PCB layers are separated, usually exposing or damaging the wiring.

Pad stripping: The pad is detached from the surface during welding or reworking.

Causes: Excessive etching during manufacturing, overheating during welding, or mechanical stress (such as bending or vibration).

Impact: Open circuit or connection is not reliable, so that part of the board can not work

#04

short-circuit

Description:

An unexpected electrical connection between two points on a PCB, usually caused by a manufacturing defect or design error

Up.

Example:

Welded bridge: As mentioned earlier, excess solder is attached to adjacent pins.

Copper Whisker: Manufacturing residues cause tiny copper wires to grow from the wiring, bridging gaps.

Insufficient Spacing: Wires or pads are placed too close together during the design phase.

Reasons: Insufficient PCB layout spacing, poor solder mask application or contamination during manufacturing.

Impact: Overheating, component damage, or complete system failure.

#05

Open a way

Description:

Circuit path interrupts prevent the flow of current and are usually subtle and difficult to detect.

Example:

Incomplete wiring: There is a gap in the wiring due to insufficient etching or error.

Through hole failure: Plating through holes (through holes) cannot connect layers due to drilling or plating problems.

Lead break: The lead breaks due to mechanical stress or poor welding.

Causes: manufacturing errors (such as inconsistencies in etching), thermal stress, or physical damage during handling.

Affected: Part of the affected circuit loses function.

#06

Environmental and material degradation

Description:

External factors or material quality issues cause PCB degradation from time to time or during operation.

Common problems:

Corrosion: Oxidation of copper wires or solder joints due to moisture or chemical exposure.

Thermal damage: Overheating causes warping, delamination or cracking of solder joints.

Electromigration: The high current density causes the metal atoms in the wire to move and gradually thin.

Causes: poor environmental control (e.g. humidity, temperature), low quality substrate material or overheating during operation.

Impact: Shortened life, intermittent failure, or complete breakdown.

#07

Design related problem

Description:

Errors in PCB layout or design stage, which appear during manufacturing or use.

Example:

Insufficient cable width: The cable is too thin to withstand the current, resulting in overheating or burning.

Poor heat management: Lack of heat sink or over hole heat dissipation, resulting in component failure.

Electromagnetic interference (EMI): Signal noise caused by improper wiring or grounding.

Reasons: insufficient design validation, ignoring electrical/thermal requirements, or skipping simulation steps.

Impact: Performance degradation, reliability issues, or the need for expensive design modifications

#08

Manufacturing defect

Description:

A defect that does not exist in the design introduced during manufacturing or assembly.

Common problems:

Drilling misalignment: Through holes or component holes are drilled incorrectly, causing layer misalignment.

Solder mask problems: The mask is incomplete or incorrectly applied, exposing the wiring and possibly causing a short circuit.

Warping: The sheet bends during lamination due to uneven heating or improper material selection.

Cause: equipment calibration error, operation error or inconsistent process control.

Impact: Boards may fail tests or perform unreliably in the field.

#09

PCB FAQ summary